Hardly a real problem, but maybe a code review reveals more: when using Google Chrome and having unbalanced HTML tags in a post (tags for which no matching opening or closing tag is found) then hitting Ctrl-B or Ctrl-I (or Command-B or Command-I) somewhere in the post, inserts additional brackets.

On my Mac, this only happens in Chrome, not in Safari nor Firefox. It only occurs for allowed tags, like <pre>, <b> or <i>, but not for <u> or <blink>. The toolbar buttons do not get confused. When the unbalanced tags are in code blocks or within backticks, then all is fine too.